Gamma Cephei

This article is about the star. For the Tunisian newspaper, see Erraï.
Gamma Cephei

Location of γ Cephei (top center)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cepheus
Right ascension 23h 39m 20.910s[1]
Declination +77° 37′ 56.51″[1]
Apparent magnitude (V) 3.21[2]
Characteristics
Gamma Cephei A
Spectral type K1III-IV CN1[3]
U−B color index +0.94[2]
B−V color index +1.03[2]
Variable type Suspected[4]
Gamma Cephei B
Spectral type M4V[5]
Astrometry
Radial velocity (Rv)−42.82±0.30[6] km/s
Proper motion (μ) RA: –64.860 mas/yr[1]
Dec.: 171.159 mas/yr[1]
Parallax (π)72.5167 ± 0.1470 mas[1]
Distance44.98 ± 0.09 ly
(13.79 ± 0.03 pc)
Absolute magnitude (MV)2.62[7]
Orbit[8]
PrimaryA
CompanionB
Period (P)66.84±1.32 yr
Semi-major axis (a)1.419±0.012"
(19.56±0.18 AU)
Eccentricity (e)0.4144±0.0066
Inclination (i)120.18±0.27°
Longitude of the node (Ω)18.32±0.78°
Periastron epoch (T)1991.581±0.048
Argument of periastron (ω)
(secondary)		340.49±0.50°
Semi-amplitude (K1)
(primary)		1.898±0.014 km/s
Details[9]
Gamma Cephei A
Mass1.27+0.05
−0.07 M☉
Radius4.74+0.03
−0.08 R☉
Luminosity11.6±0.6[10] L☉
Surface gravity (log g)3.18 cgs
Temperature4,806±60 K
Metallicity [Fe/H]0.20±0.07 dex
Rotational velocity (v sin i)1.63[6] km/s
Age5.7+0.8
−0.9 Gyr
Gamma Cephei B
Mass0.328+0.009
−0.012 M☉
Other designations
Errai, 35 Cep, BD+76°928, FK5 893, HD 222404, HIP 116727, HR 8974, SAO 10818
Database references
SIMBADdata
Exoplanet Archivedata

Gamma Cephei (γ Cephei, abbreviated Gamma Cep, γ Cep) is a binary star system approximately 45 light-years away in the northern constellation of Cepheus. The primary (designated Gamma Cephei A, officially named Errai /ɛˈreɪ.iː/, the traditional name of the system)[11][12] is a stellar class K1 orange giant or subgiant star; it has a red dwarf companion (Gamma Cephei B). An exoplanet (designated Gamma Cephei Ab, later named Tadmor) has been confirmed to be orbiting the primary.

Gamma Cephei is the naked-eye star that will succeed Polaris as the Earth's northern pole star, due to axial precession. It will be closer to the northern celestial pole than Polaris around 3230 CE and will make its closest approach around 4300 CE. The 'title' will pass to Iota Cephei some time around 5200 CE.

  1. ^ a b c d Cite error: The named reference GaiaDR3 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference bsc was invoked but never defined (see the help page).
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  4. ^ Cite error: The named reference gcvs was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Neuhäuser2007 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference jofre was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference park2013 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Mugrauer2022 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Knudstrup was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Baines2018 was invoked but never defined (see the help page).
  11. ^ Rumrill, H. B. (June 1936). "Star Name Pronunciation". Publications of the Astronomical Society of the Pacific. 48 (283). San Francisco, California: 139. Bibcode:1936PASP...48..139R. doi:10.1086/124681. S2CID 120743052.
  12. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.